Brendan Doyle

Program Overview for Dr. Brendan Doyle, PhD

Brendan Doyle, Rehabilitation Science PhD graduate

Mentor: Dave Fuller, PhD, professor, Department of Physical Therapy

Graduation Date: Fall 2019

Future Plans: Dr. Doyle has accepted a tenure track position as an Assistant Professor of Biology at Quincy University in Quincy, Illinois for fall 2020.

Dissertation Title: Delivering Genes to the Hypoglossal Motor System

Dissertation Abstract:

The hypoglossal (XII) motor system (XII motor pool, XII nerve and tongue musculature) provides an excellent candidate to study gene transfer and gene therapy vector administration. The experiments presented here were conducted using adult C57-b, SVE129 and Gaa-/-(SVE129) mice and adult Sprague-Dawley rats. All experiments were performed with approval from the University of Florida Institutional Animal Care and Use Committee.

Aim 1 was to optimize gene delivery to the XII nucleus via intralingual delivery of adeno-associated virus serotype 9 (AAV9) in the adult mouse and adult rat. Mice and rats received intralingual injections of AAV9. Results demonstrate that intralingual injection of AAV9 produces transgene expression in XII motoneurons of adult mice and rats and can be optimized with the appropriate dose and injection volume.

Aim 2 was to determine the efficacy of intramuscular delivery of an AAV9 for targeted delivery of an enhanced form of acid-alpha glucosidase (GAA) to tongue myofibers and motoneurons in 6-mo old Pompe (Gaa-/-) mice. Mice received an intralingual injection of AAV9 encoding either the enhanced or native enzyme; tissues were harvested 4 months later. Both AAV9 constructs effectively drove GAA activity in lingual myofibers, and both drove GAA expression in tongue motoneurons. However, mice treated with the AAV9 constructs encoding the enhanced GAA enzyme had a >200% increase in the number GAA positive motoneurons.

Aim 3 was to deliver genes to the XII nucleus in the adult rat via direct XII nerve injection. Animals received a direct XII nerve injection of AAV9-mCherry or wheat germ agglutinin Texas Red X Conjugate (WGA-TxRed) for comparison to AAV9. Unilateral direct XII nerve injection of AAV9-mCherry produced robust, bilateral transgene expression in XII motoneurons, while WGA-TxRed produced robust unilateral tracer expression.

Overall, the results of these experiments indicate that the XII motor system is an excellent system to study gene delivery utilizing AAV9. Intramuscular delivery of AAV9 can successfully deliver both tracer and therapeutic transgenes to XII motoneurons in the adult mouse. In the adult rat, intramuscular injection is only modestly effective while direct XII nerve injection is highly effective at delivering transgenes to XII motoneurons.


Doyle BM, Turner SMF, Sunshine MD, Doerfler PA, Poirier AE, Vaught LA, Jorgensen ML, Falk DJ, Byrne BJ, Fuller DD, AAV gene therapy utilizing glycosylation-independent lysosomal targeting tagged GAA in the hypoglossal motor system of Pompe mice, Molecular Therapy: Methods & Clinical Development (2019), doi: j.omtm.2019.08.009.

Doyle, T., & Doyle, B., (2018) Learning in Harmony with Your Brain in Routledge Handbook on Student Centered Learning, London: Routledge Publishing

Select Honors and Awards

Supplemental Retention Scholarship, Graduate School, UF Fall 2019

Graduate Fellowship Award, Rehabilitation Science Program, PHHP, UF 2015-2019

Graduate Student Travel Award, Rehabilitation Science Program, Spring 2017, Fall 2018, Spring 2019

International Mentoring Conference Spring funded by Rehabilitation Science Program, Spring 2019